Association of age-related decrease in intracellular-to-total water ratio with that in explosive strength of the plantar flexors: a cross-sectional study

Segmental extracellular-to-intracellular water resistance ratio and physical function in older adults

OBJECTIVES

This study aimed to investigate the association between whole-body (WB), arm, and leg extracellular-to-intracellular water resistance (Recw/Ricw) ratios and various physical functions of each segment and muscle mass using segmental multifrequency bioelectrical impedance analysis.

METHODS

In total, 988 community-dwelling older adults were included in the analysis. Physical function was assessed using hand grip, 5-repetition sit-to-stand, 5-m habitual walk, Timed Up and Go, and single-leg balance with eyes open tests. Each segmental Recw/Ricw ratio and muscle mass were assessed at 5 and 250 kHz resistances using a segmental multifrequency bioelectrical impedance analysis device. Pearson's correlation between the segmental Recw/Ricw ratio and muscle mass and physical function was calculated, and the difference in correlation coefficients was tested using Bonferroni correction. Multiple linear regression analysis was conducted using physical function as the dependent variable and the segmental Recw/Ricw ratio as the independent variable, adjusting for sex, age, body mass index, and segmental muscle mass.

RESULTS

WB and leg Recw/Ricw ratios were significantly positively correlated with good hand grip performance, gait speed, mobility, balance, and standing power (p < 0.05), after adjusting for sex, age, body mass index, and muscle mass. Furthermore, the leg Recw/Ricw ratio was positively associated with lower extremity physical function compared with WB and arm Recw/Ricw ratios and muscle mass (p < 0.01). Conversely, WB muscle mass was more strongly related to grip strength than WB, arm, and leg Recw/Ricw ratios (p < 0.01).

CONCLUSIONS

The Recw/Ricw ratio is useful for identifying older adults with worse physical function. The Recw/Ricw ratio allows for easy and timely screening of older adults with worse physical function in clinical settings.

Prediction of the Risk of Bone Mineral Density Decrease in Type 2 Diabetes Mellitus Patients Based on Traditional Multivariate Logistic Regression and Machine Learning: A Preliminary Study

Purpose

There remains a lack of a machine learning (ML) model incorporating body composition to assess the risk of bone mineral density (BMD) decreases in type 2 diabetes mellitus (T2DM) patients. We aimed to use ML algorithms and the traditional multivariate logistic regression to establish prediction models for BMD decreases in T2DM patients over 50 years of age, and compare the performance of the two methods.

Patients and Methods

This cross-sectional study was conducted among 450 patients with T2DM from 1 August 2016 to 31 December 2022. The participants were divided into a normal BMD group and a decreased BMD group. Traditional multivariate logistic regression and six ML algorithms were selected to construct male and female models. Two nomograms were constructed to evaluate the risk of BMD decreases in the male and female T2DM patients, respectively. The ML models with the highest area under the curve (AUC) were compared with the traditional multivariate logistic regression models in terms of discriminant ability and clinical applicability.

Results

The optimal ML model was the extreme gradient boost (XGBoost) model. The AUCs of the traditional multivariate logistic regression and the XGBoost models were 0.722 and 0.800 in the male testing dataset, respectively, and 0.876 and 0.880 in the female testing dataset, respectively. The decision curve analysis results suggested that using the XGBoost models to predict the risk of BMD decreases obtained more net benefits compared with the traditional models in both sexes.

Conclusion

We preliminarily proved that the XGBoost models outperformed most other ML models in both sexes and achieved higher accuracy than traditional analyses. Due to the limited sample size in the study, it is necessary to validate our findings in larger prospective cohort studies.

Association of appendicular extracellular-to-intracellular water ratio with age, muscle strength, and physical activity in 8,018 community-dwelling middle-aged and older adults

BACKGROUND

The appendicular extracellular-to-intracellular water ratio (Ap ECW/ICW) has recently gained attention as a non-invasive measurable marker of muscle quality. However, there is a lack of basic evidence regarding age-related changes, sex differences, contribution to muscle strength independent of skeletal muscle mass (SMM), and potential improvement through physical activity (PA) in Ap ECW/ICW.

METHODS

This cross-sectional study enrolled 8,018 middle-aged and older Japanese individuals (aged 45-75 years). The Ap ECW/ICW and SMM were measured using segmental bioelectrical impedance spectroscopy. Muscle strength was evaluated by measuring the handgrip strength (HGS) with a dynamometer, and the PA level (PAL) was measured with an accelerometer. We performed a linear regression analysis of the associations of the Ap ECW/ICW with age, HGS, and PAL.

RESULTS

The Ap ECW/ICW increased by 0.019 for men and 0.014 for women per 5-year increase in age (p < 0.001), and the age-related increase was greater in men than in women (p for interaction <0.001). The Ap ECW/ICW was more strongly associated with the HGS than with the SMM in both men and women (p < 0.001). PAL showed a significant inverse association with the Ap ECW/ICW in both men and women (p < 0.001).

CONCLUSIONS

Ap ECW/ICW is higher with age, and it varies by sex. The Ap ECW/ICW may reflect muscle strength more than the SMM, suggesting that the Ap ECW/ICW may be improved by PA. The findings from this study may provide a framework for further Ap ECW/ICW research.

Can phase angle from bioelectrical impedance analysis associate with neuromuscular properties of the knee extensors?

Maintenance and improvement of neuromuscular functions is crucial for everyone regardless of age. An easy way to assess neuromuscular properties without muscle contraction is useful especially for those who cannot perform strenuous muscular force production, such as older adults and patients with orthopedic or cognitive disorders. Bioelectrical impedance analysis (BIA) can assess body electrical properties e.g., phase angle (PhA) which is regarded as muscle quantity/quality index. The purpose of this study was to investigate associations of PhA with neuromuscular properties of the knee extensors in 55 young (n = 23) and older (n = 32) adults. The values of PhA of the right thigh and whole-body were determined with BIA at 50 kHz. The participants performed 4-s maximal voluntary isometric contraction (MVIC) to measure peak torque (PT_MVIC), and 1-s brief MVIC to assess rate of torque development (RTD) over the time interval of 0–200 ms. As markers of physiological mechanisms of muscle force production, twitch contractile properties (peak twitch torque, rate of twitch torque development, and time-to-peak twitch torque) of the knee extensors obtained by femoral nerve electrical stimulation, and muscle activity assessed as root mean square values of electromyographic activity (EMG-RMS) during PT_MVIC and RTD measurements were measured. Thigh and whole-body PhA significantly correlated with PT_MVIC (r ≥ 0.555, p < 0.001) and electrically evoked twitch parameters (peak twitch torque, rate of twitch torque development, and time-to-peak twitch torque; |r| ≥ 0.420, p ≤ 0.001), but not RTD (r ≤ 0.237, p ≥ 0.081) or EMG-RMSs (|r| ≤ 0.214, p ≥ 0.117). Stepwise multiple linear regression analysis revealed that thigh PhA was selected as a significant variable to predict PT_MVIC but not RTD. Whole-body PhA was not selected as a significant variable to predict PT_MVIC or RTD. In conclusion, both thigh and whole-body PhA can associate with maximal voluntary muscle strength of the knee extensors, and this association may be due to intrinsic contractile properties but not neural aspects. Regarding prediction of the knee extensor strength, thigh PhA is preferable as the predictor rather than whole-body PhA which is used as a widely acknowledged indicator of sarcopenia.

Muscle quality indices separately associate with joint-level power-related measures of the knee extensors in older males

PURPOSE

The purpose of this study was to investigate associations of muscle quality indices with joint-level power-related measures in the knee extensors of thirty-two older males (65-88 years).

METHODS

Muscle quality indices included: echo intensity, ratio of intracellular- to total water content (ICW/TW), and specific muscle strength. Echo intensity was acquired from the rectus femoris (EI_RF) and vastus lateralis (EI_VL) by ultrasonography. ICW/TW was computed from electrical resistance of the right thigh obtained by bioelectrical impedance spectroscopy. Specific muscle strength was determined as the normalized maximal voluntary isometric knee extension (MVIC) torque to estimated knee extensor volume. Isotonic maximal effort knee extensions with a load set to 20% MVIC torque were performed to obtain the knee extension power-related measures (peak power, rate of power development [RPD], and rate of velocity development [RVD]). Power and RPD were normalized to MVIC.

RESULTS

There were no significant correlations between muscle quality indices except between EI_RF and EI_VL (|r|≤ 0.253, P ≥ 0.162). EI_RF was negatively correlated with normalized RPD and RVD (r ≤  - 0.361, P ≤ 0.050). ICW/TW was positively correlated with normalized peak power (r = 0.421, P = 0.020). Specific muscle strength was positively correlated with absolute peak power and RPD (r ≥ 0.452, P ≤ 0.012).

CONCLUSION

Knee extension power-related measures were lower in participants with higher EI, lower ICW/TW, and lower specific muscle strength, but the muscle quality indices may be determined by independent physiological characteristics.